This invention relates to a keyboard apparatus for an electronic musical instrument, particularly an electronic piano.
A conventional electronic piano comprises jacks and hammers, each being rotatably supported by a shaft and a complete bearing. It is thus so arranged that each jack is returned to its original position by means of a spring and that each hammer is returned to its original position by its own weight.
In addition, the conventional electronic piano has the following arrangement. Namely, a first switch portion and a second switch portion of each of keyboard switches are sequentially operated or actuated by an actuator provided on a key so that a sound is generated in a sound volume depending on the time from the actuation of the first switch portion to the actuation of the second switch portion.
According to the above-mentioned conventional arrangement of the electronic piano, there is a disadvantage in that the number of assembling steps is large because the jacks and the hammers are rotatably supported by shafts and complete bearings.
In addition, according to the above-mentioned arrangement of the conventional electronic piano, since the keyboard switches have dimensional errors in manufacturing, when an attempt is made to stabilize the sound volume corresponding to the velocity of depressing the key, the difference in stroke between the first switch portion and the second switch portion of the keyboard switch at the front of the key cannot be made narrower than a certain value, but has to be kept large. As a consequence, the conventional electronic piano has a poor performance or efficiency in depressing a key in rapid succession (hereinafter called "a rapid successive key depression efficiency"). In addition, it has a disadvantage in that it is difficult to generate a sound in a light-depression playing, i.e., by playing the electronic piano in such a way of piano playing as depressing the key half way down first, followed by its further depression.